DIY Heat Treat Oven Help - Will not warm

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Kovecs

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Jan 17, 2025
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Hey all, looking for some help chasing down gremlins in a diy heat treat oven. It was built off the below video and wiring diagram (with the exception that I'm using 120v and different heating elements to bring the total resistance down to about 7 ohm). Everything in the control box seems to be functioning properly, heating element wires are live, and thermocouple is accurately reading ambient temperature, but the oven just refuses to heat at all. Not sure if this is an ID10T error due to screwing something up with the PID programming, or another issue. Any help is appreciated, thanks!

Oven Build Guide
https://imgur.com/a/EfILBbp
 
Have you set the target temp and hit RUN?

OK, I had to ask.

Most likely issue is the control wires to the SSR. Check the two switches in those lines. Make sure the + and - are not switched on one SSR.
Check the thermocouple polarity. It and any wires used to hook it up are positive and negative and made of different metals.
 
Check your wiring all over. Make sure something didnt get crossed polarity wise, or get loose and get off a terminal. So the SSR's light up?

Are you using the exact same PID? What settings?
 
Taz said:
Check your wiring all over. Make sure something didnt get crossed polarity wise, or get loose and get off a terminal. So the SSR's light up?

Are you using the exact same PID? What settings?
Click to expand...
I'm now realizing neither of the SSR's lit up at all, red or green. I'll chase the wire routes as soon as I'm back in the shop this weekend--ditto for the comment above.
 
When I first built my oven I ordered a SSR without reading the description and it was a DC SSR which didnt work at all
 
Do you have a picture of your control box wiring? It will be a bit different using 120V than a 240V set up!

I did a 120V control box for a kiln I had, so the power to the elements was basically the Kiln plugged into the power plug going out from the box. I didn't use any fuses or door/element kill switches. Power in to power the PID itself, PID outputs to the SSR, SSR to the plug to control the elements.

If you used door/element switches, check to make sure they are wired correctly, too and not reversed! A door or element switch could be wired incorrectly (normally closed vs normally open). It's super easy to switch one wire around and nothing works right!
 
Those are my suspects too - the two switches.


WAIT!
I just looked at his info and am not sure if he wired a 120V circuit as a 220 V circuit. There are many issues there. there is no need for the second SSR. The coil will have a different resistance for 120V than 220V.
The plug shown is a 220V plug? The two SSRs indicate two hot legs? Where do you live?
 
Last edited:
Yeah, RedBeards is 240V, 2 SSR, Door switch on one leg, element kill switch on other leg, etc. He linked the RedBeard wiring diagram in his post.

A 120V wiring setup will be very different from a 240V setup!
 
Stacy E. Apelt - Bladesmith said:
Those are my suspects too - the two switches.


WAIT!
I just looked at his info and am not sure if he wired a 120V circuit as a 220 V circuit. There are many issues there. there is no need for the second SSR. The coil will have a different resistance for 120V than 220V.
The plug shown is a 220V plug? The two SSRs indicate two hot legs? Where do you live?
Click to expand...
I may need to backtrack and just rewire power for 240 given I probably dorked up tue conversion per your post
 
Before you change anything....

Let's start with fresh info:
1) What voltage is the oven running on? ( You said 120, and now 220???)
2) Where do you live? (Some countries have different power phases)
3) Is the schematic linked your plan or one that you used as a guide? (We need to know exactly how you wired your oven.)
4) Post a photo of your kilns control box and a schematic of your build.
 
The schematic linked is Red Beards....I saved the same one when I was going through my build this past summer.
 
Yup, but he initially said he only changed the voltage and resistance. We need to know the exact wiring diagram used.

"It was built off the below video and wiring diagram (with the exception that I'm using 120v and different heating elements to bring the total resistance down to about 7 ohm)."
 
Kovecs said:
I may need to backtrack and just rewire power for 240 given I probably dorked up tue conversion per your post
Click to expand...
I think he's saying he wired for 120vac originally, and now will just "rewire" for 240vac to allow him to follow the wiring diagram exactly.
 
I just saw something on the diagram of the circuit that could be the problem. While the + and - on the SSRs are shown properly connected as a schematic, they are actually crossed if the image is actual parts placement. If you rotate one of the SSRs so the control contacts 3 and 4 face each other as in the diagram, +/- are not straight across from each other, You would wire across to the other +/- terminals, not straight as in the diagram. Look closely at your wiring and assure positive terminal 3 is connected to the other terminal 3 and negative 4 to 4.
 
Hey folks sorry for a lengthy delay--have been out of the shop. Got everything rewired for 220v and the SSRs are still not lighting up, and no heating is occurring. I've chased all the wires but am clearly still missing something--I've attached photos of my actual control box wired
https://imgur.com/a/zqX2xhL
 
I see it! The TC wires are backwards. Red is negative on a type K TC. Yellow is positive.
 
Yes it matters. The wires are bi-metal, just like the TC. It will make the TC read wrong.

I also think there is something else wrong.
It looks like the element switch is not wired right, as I see no light. It could be that the terminals were not connected right. Double check that the terminal for the light was not accidentally mixed up with the on-off terminals. That is more likely to be where the issue is.

I would take a meter and set it on AC, ground one lead, and follow the power to see where it stops. It should go to both SSRs. I'm pretty sure that is OK.
Then attach one terminal to the negative SSR terminal at the PID and trace it. with the meter set on DC, and trace the trigger positive voltage from the PID to the +/- of the SSRs. It should be there all the way.
 
My element switch and red beards element switch do not light up either. We're only using it to break the current so we'd have to add in another wire to get the light to actually function.
 
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